HELP PLEASE syncing w/o losing itunes downloaded to ipod

Hi guys!
I'd really appreciate your help...
I have an 8g ipod touch. I've downloaded approx. 30 itunes directly onto my ipod. I dont have a copy of the songs on my itunes on my laptop since I bought them directly with my ipod. I wanted to add some music/hotos etc. from my laptop to my ipod but I'm afraid if I sync my ipod with these files though my laptop I might loose my existing itunes songs that I bought?
If I sync my ipod will I lose these songs? or will it just add the additional files?
I havnt tried it since I was afraid of losing the songs.
Any input would be greatly appreciated!
Thanks!

It shouldn't do anything to those songs. But to make absolutely sure, plug in your iPod. Go to File > Transfer Purchases from [Your iPod's Name Here]. Click on that, and it'll copy those songs onto your computer.